Fabrication and oxidation behavior of Al ₄ SiC ₄ powders

Abstract

Abstract Al 4 SiC 4 powders with high purity were synthesized by heating the powder mixture of aluminum (Al), silicon (Si), and carbon (C) at 1800°C in argon. The microstructure is characterized as platelike single grain. Both the nonisothermal and isothermal oxidation behavior of Al 4 SiC 4 was investigated at 800°C‐1500°C in air by means of thermogravimetry method. It is demonstrated that Al 4 SiC 4 powder possesses good oxidation resistance up to 1200°C and is almost completely oxidized at 1400°C. At 800°C‐1100°C, the oxide scales consist of an Al 2 O 3 outer layer and a transition layer. Al 4 SiC 4 remains the main phase. At 1200°C, some spallation resulting from the increment of Al 2 O 3 and the mismatch of thermal expansion coefficient between different product layers can be observed. Above 1300°C, the oxide layer is composed of two part, i.e., large‐scale Al 2 O 3 crystals (outer layer) and mullite with less amount of SiO 2 (inner layer). The oxidation behavior changes due to the different oxide products. For the reaction kinetics, a new kind of real physical picture model is adopted and obtains a good agreement with the experimental data. The apparent activation energy is calculated to be 176.9 kJ/mol (800°C‐1100°C) and 267.1 kJ/mol (1300°C‐1400°C).